Eurocopter said it was issuing a safety notice to remind all EC 135 operators to follow the safety procedures already in place and outlined in the flight manual, regardless of the aircraft's fuel quantity indication.

The company said it would "update its Safety Information Notice as needed" with investigations continuing.

Bond Aviation said in a statement on Monday that the results of the tests on the rest of its helicopters were validated by Eurocopter, and appropriate repairs were made before returning the aircraft to service.

The discovery of the fault in Bond's fleet came 12 days after one of its EC 135s leased to Police Scotland crashed into the Clutha pub in Glasgow killing three crew members and seven people inside the pub.

The helicopter was only minutes away from returning to its base when it dropped vertically onto the roof of the bar.

A preliminary report from the Air Accidents Investigation Branch found no major engine or gearbox problems with the police helicopter.

It also found that the aircraft had sufficient fuel when it crashed at 22:25 on 29 November.